Published online by Cambridge University Press: 15 February 2011
The c-axis sound velocities and attenuations for HOPG, stage 3 and stage 4 SbCl5-graphite were determined by ultrasonic techniques in the temperature range between 4 and 325 *K. The temperature variation of C33 for HOPG agrees closely with the theoretical prediction based on the Lennard-Jones interlayer potential. In SbCl5-graphite, the longitudinal sound attenuation increases sharply and the transverse sound cannot propagate for temperatures above 200 °K, indicating a commensurate-to-incommensurate in-plane phase transition. The stage dependence of C33 at low temperatures indicates that the interlayer forces beyond the nearest layers can not be neglected.